20 1 1 how to solve the tenth question of Wuhan mathematics test, please, please, be more detailed, thank you.
The cosine theorem in triangle can get an equation, and the two solutions are the lengths of JG and JF, which need to be deformed. The sum and product of two roots can get the difference between the two roots, and the length of FG can be obtained by dividing it by 20m\s (chemical unit), and the result is B.